SAN DIEGO — Pharmacologic prophylaxis can sharply reduce the risk of deep venous thrombosis when cancer patients undergo surgery, Dr. Michael J. Leonardi said at a symposium sponsored by the Society of Surgical Oncology.
The deep venous thrombosis (DVT) rate falls from 35% without prophylaxis to 12% when surgical oncology patients are given heparin, according to Dr. Leonardi of the University of California, Los Angeles. A combination of mechanical prophylaxis with heparin further reduces the DVT rate to just 5%.
“Cancer patients need some form of prophylaxis,” Dr. Leonardi said in an interview after his review of data from dozens of randomized, controlled trials. “If bleeding risk is not a concern,” he added, “pharmacological prophylaxis is better than mechanical prophylaxis, and combination therapy has been shown to be even more effective.”
Dr. Leonardi and his colleagues in the UCLA surgery department searched the Medline database for English-language trials and found 55 randomized controlled trials published from 1966 to 2005 on DVT prophylaxis in general surgery. Among these, 26 trials reported outcomes for 7,639 cancer patients, Dr. Leonardi said.
Colorectal and major abdominal surgical procedures accounted for 39% and 38% of cases, respectively. Upper gastrointestinal and small bowel operations were the next most common at 11%, followed by gynecologic surgery at 3%. Biliary, pancreatic, urologic, and noncardiac thoracic cancers each accounted for just 1% of the surgical procedures in Dr. Leonardi's presentation.
After a review of the wide variety of patients and surgeons in these trials, he said the best prophylaxis for individual cancers is still not known. For example, not even one randomized controlled trial was found that evaluated DVT prophylaxis in breast cancer patients. The incidence of DVT in breast cancer “is probably not as high as in some other cancers, but because breast cancer is so common a lot of DVTs are associated with it,” he said.
Among the findings from the analysis, Dr. Leonardi reported that:
▸ DVT rates vary with the detection method used. Venography was the most sensitive method, and ultrasound the least sensitive.
▸ Higher heparin doses are more effective than lower doses. DVT rates were 8% for higher doses and 14% for lower doses of the forms of heparin in 17 trials with a total of 4,005 patients.
▸ Low-molecular-weight heparin and low-weight unfractionated heparin are equally effective. Both cut DVT rates to 8% at high doses in the 17 trials just cited. At low doses, the rate was 14% for low-molecular-weight heparin and 13% for low-weight unfractionated heparin.
▸ Heparin reduces the rate of proximal DVTs. The rate went from 41% to 13% in nine trials reporting on 284 patients with DVTs. Location was unaffected by the use of low-molecular-weight heparin vs. low-weight unfractionated heparin.
▸ Major complications occur in only 1% of cases with pharmacologic prophylaxis. Based on seven trials, minor complications occurred in 10% of patients and major complications in 1%, he reported. There was no difference between low-molecular-weight heparin and low-weight unfractionated heparin. In four trials, 3% of patients discontinued prophylaxis.